Compact service module and use thereof in a plant for producing aluminum by electrolysis

ABSTRACT

A pot tending module for an aluminum production plant comprising a frame and a rotary part including a hopper mounted on said frame so as to pivot about a substantially vertical axis, said rotary part being equipped with at least one tool mounted on a telescopic arm, said pot tending module comprising a first bearing structure to carry all of said rotary part mounted on said frame so as to be pivotable about a substantially vertical axis, a fixed member of said telescopic arm being mounted on a second bearing structure of said rotary art through attachment means fixed to an attachment part of said fixed member placed between the ends of said fixed member. A pot tending machine, a port tending assembly comprising the pot tending module described above, and use of said pot tending assembly.

SCOPE OF THE INVENTION

The invention relates to aluminum production using igneous electrolysis by means of the Hall-Héroult process. It more particularly relates to pot tending modules used in aluminum production plants.

BACKGROUND OF RELATED ART

Aluminum is produced industrially by igneous electrolysis in electrolytic cells according to the well-known Hall-Héroult process. The plants contain a great number of electrolytic cells laid out in line, in buildings called electrolysis halls or rooms, and electrically connected in series using connecting conductors. The cells are generally laid out so as to form two or more parallel lines which are electrically linked to each other by end conductors.

When operating, an electrolysis plant requires work on the electrolytic cells, including replacement of spent anodes by new ones, sampling of molten metal in the cells and sampling or top-ups of electrolyte. In order to carry out this work, the most modern plants are equipped with one or more pot tending assemblies including an overhead traveling crane which can be translated above the series of electrolytic cells, and one or more pot tending machines each comprising a carriage and a pot tending module provided with handling and servicing devices (often called “tools”) such as shovels and hoists, able to be moved on the overhead traveling crane. These assemblies are often called “Pot Tending Assemblies” (PTA) or “Pot Tending Machines” (PTM).

In order to optimize the space in the electrolysis halls and reduce the cost of investment, the electrolytic cells are laid out as close as possible to each other and close to one of the lateral sides of the electrolysis halls and an aisle as narrow as possible is made close to the other lateral side of the halls. This layout requires that the distance between the walls of the electrolysis hall and the limits of the workspace of each pot tending machine tool is as small as possible, especially for access to the electrolytic cells. This distance is called the “tool approach” distance. The position of the cells in the electrolysis hall and the total area of the hall that results from this is greatly dependent on the volume occupied by the pot tending machines and the possibilities of approaching and moving their tools. However, known pot tending modules occupy a large volume that makes it impossible to get close to the sides of electrolysis halls, particularly the lateral sides, and which significantly reduces their movements close to these sides. The volume of the modules can be reduced by bringing the tools closer together. However, this solution may increase the risk of damaging the tools during maintenance operations.

European patent EP 1781839 by the applicant proposes a pot tending module comprising a frame able to be secured to a carriage and a turret mounted on said frame so as to pivot about a vertical axis, said turret being equipped with a plurality of handling and service members. This pot tending module includes a set of tools mounted on telescopic arms, each telescopic arm being fixed to the turret by an articulated support allowing pendular movements of said telescopic arm with respect to a determined point of articulation. In this pot tending module, the telescopic arms are interconnected by a mechanical connecting device to maintain, within a determined tolerance range, the relative angular difference between the pendular movements of said telescopic arms. Such a pot tending module makes it possible to bring the tools closer together, thus limiting the volume, especially the width, under the frame of said module. It also give the tools a limited independence of movement, while preventing them from colliding with each other and preventing any jolts undergone by one of the tools from having a direct impact on the other tools.

A technical problem with the pot tending module of prior art is to further minimize the volume under the frame of the module, including the height under the frame of the pot tending module, and the volume of space covered by the entire pot tending module during rotation of its rotary part.

DESCRIPTION OF THE INVENTION

One subject of the invention relates to a pot tending module for use in a plant for producing aluminum by igneous electrolysis, said module comprising a frame able to be secured to a carriage and a rotary part mounted on said frame so as to pivot about a substantially vertical axis, said rotary part being equipped with at least one tool mounted on a telescopic arm of said rotary part, said pot tending module further comprising a first bearing structure mounted on said frame and designed to bear a hopper, said pot tending module being characterized in that said first bearing structure and said hopper are included in said rotary part, said first bearing structure being designed to bear the entire said rotary part and being mounted on said frame so as to pivot about said substantially vertical axis, and in that said rotary part comprises a second bearing structure, a fixed member of said telescopic arm being mounted on said second bearing structure interdependent with said rotary part through attachment means allowing pendular movements of said telescopic arm, said attachment means being fixed to an attachment part of said fixed member placed at a distance from the ends of said fixed member.

Most often, the pot tending module is mounted on the carriage of a pot tending machine, said carriage being, in turn, mounted on the overhead traveling crane of a pot tending assembly which may be translated above the electrolytic cells. The rotary part of the pot tending module is therefore generally placed or suspended below the carriage, i.e. still under the frame of said pot tending module. More specifically, this rotary part is usually mounted rotatably on the frame so as to be able to rotate, most often around itself, about a substantially vertical axis. In the following, this rotary part can also be called a turret.

As the first bearing structure is designed to bear all of said rotary part and is mounted on said frame so as to pivot about said substantially vertical axis, this first bearing structure is therefore generally the upper part of said rotary part.

The rotary part is normally equipped with a determined set of tools, each tool element of said assembly being mounted on a telescopic arm attached to the second bearing structure. The telescopic arms on which the tools are mounted, the second bearing structure, and the attachment means placed between the second bearing structure and the telescopic arms are all included in the rotary part. This determined set of tools may typically comprise at least one tool selected from a crust shovel, an anode handling clamp and a crust breaker.

In one aspect of the invention, the hopper is within the rotary part or turret. The rotary part therefore comprises not only the tools and telescopic arms on which they are mounted, but also the hopper. This hopper, which supplies the electrolytic cell with products in powder form, generally has a large volume compared with the tools and telescopic arms on which they are mounted. The inclusion of this hopper in the rotary part makes it possible to minimize the volume under the frame of said module, or more precisely the volume of the area covered by the entire pot tending module during rotation of its rotary part, and in particular the radial extent relative to the substantially vertical axis about which said rotary part is pivotally mounted.

In the following, the volume of the area covered by the entire pot tending module during rotation of its rotary part, and in particular during a full 360° rotation of said rotary part, can be described as the spatial requirement. So in other words, the inclusion of the hopper in the rotary part optimizes the overall space required, under the frame, by the pot tending module, and in particular the radial spatial requirements relative to the substantially vertical axis about which said rotary part is pivotally mounted. If this is not so and the hopper is fixed relative to the tools, they and their respective telescopic arms should be arranged so that their rotation is not impeded by said hopper, i.e. the tools and their respective telescopic arms should be arranged in a space having a symmetry of revolution relative to the axis of rotation of the rotary part which is outside that occupied by the hopper. This choice of including the hopper in the rotary part makes it possible to arrange the hopper, the tools and the telescopic arms on which they are mounted in a space which is generally smaller, because all of these objects rotate, at the same time, around a same axis of rotation.

According to another aspect of the invention, the fixed members of the telescopic arms on which the tools are mounted are attached to the second bearing structure, the latter being interdependent with the rotary part of the pot tending module. A fixed member of a telescopic arm generally means the hollow shaft in which a movable member carrying the tool slides, said fixed member being in this case attached to the second bearing structure. This second bearing structure, which is distinct from the first bearing structure mounted on the frame, is placed under said frame and more precisely under said first bearing structure. This second bearing structure is generally placed beneath the hopper. The second bearing structure can be advantageously constituted by a walkway placed under the hopper. In the following, the second bearing structure may be described as a walkway or as an under-hopper walkway. The walkway may carry other components than the tools, such as, for example, a hydraulic unit and electrical cabinets. This configuration in which the tools are mounted on the walkway allows maintenance operators to access the tools and the various components of the pot tending module.

In addition, the tools being mounted on the second bearing structure, the forces exerted by said tools are transferred to said second bearing structure rather than to the first bearing structure bearing the entire rotary part. The use of the second bearing structure or walkway under the hopper to fix the tools means that it is possible not to use the first bearing structure bearing the entire rotary part or turret to take up the main loads exerted by said tools. This configuration in particular makes for an overall reduction in the mass of the first bearing structure bearing the entire turret. This configuration also simplifies the construction of the first bearing structure bearing the entire turret.

In yet another aspect of the invention, the attachment means allow pendular movements of the telescopic arms on which the tools are mounted. This other aspect of the invention makes it possible not only to confer independence of movement on the telescopic arms in relation to the movement of the rotary part, but also to prevent jolts sustained by a tool from directly affecting the entire the rotary part, and the other tools carried by this rotary part.

In yet another aspect of the invention, the attachment means are fixed to an attachment portion of said fixed member arranged at a distance from the ends of said fixed member. In other words, the fixed member of the telescopic arm is not attached to the second structure by one of its ends. This aspect of the invention improves accuracy in positioning the tool. This aspect of the invention also makes it possible to raise the upper end of the fixed member to an elevation close to that of the frame. The space required under the frame is thereby reduced without the need to reduce the length of the fixed member.

The different aspects of the invention presented above therefore contribute to minimizing the space required under the frame of the pot tending module even more significantly.

In a preferred embodiment of the invention, the fixed member of the telescopic arm is connected to the first bearing structure by a mechanical connecting device that limits the amplitude of the pendular movements of said telescopic arm. In this way, the amplitude tolerance range of the pendular movements of the telescopic arm(s) is even better controlled. This tolerance range is defined with respect to the rotary part, and particularly with respect to the first bearing structure of said rotary part. Unlike the module described in European patent EP 1781839, the amplitude tolerance range of the pendular movements of the telescopic arm of a tool is not defined relative to other tools of said rotary part. The amplitude tolerance range of the pendular movements of a telescopic arm is defined more deterministically than in prior art because it no longer depends on the pendular movements of other tools.

With this configuration of the pot tending module, the axial or vertical component of the forces exerted by a tool and the telescopic arm on which it is mounted is taken up by the second bearing or walkway structure under the frame, via attachment means. As for the radial or horizontal components of these forces, these are partly taken up by the first bearing structure carrying all of the rotary part or turret under the frame, through the mechanical connecting device.

In a preferred embodiment of the invention, the attachment portion of the fixed member of the telescopic arm is at a distance D from an upper end of said fixed member greater than one tenth of the length L of said fixed member. Preferably, the distance D between the attachment portion and the upper end of the fixed member is between one quarter of length L of said fixed member and two thirds of this same length. For example, the distance D between the attachment portion and the upper end of the fixed member is equal to a half the length L of said fixed member. In this way, the accuracy and robustness of the tool are improved.

Preferably, the mechanical connecting device is mounted to connect the upper end of the fixed member to the first bearing structure. Advantageously, the mechanical connecting device comprises at least one damping system for limiting the amplitude of the pendular movements of the telescopic arm in a horizontal direction. Advantageously, the mechanical connecting device comprises two damping systems to limit the amplitude of the pendular movements of the telescopic arm in two substantially perpendicular horizontal directions.

Preferably, the upper end of the fixed member of the telescopic arm has an elevation just below that of the frame. Preferably, the part of the fixed member between its upper end and its attachment portion extends through an opening in the first bearing structure. In this way, the fixed member of the telescopic arm can extend to the frame, which makes it possible to limit the spatial dimensions under the frame of the pot tending module.

Preferably, the attachment means are designed to prevent rotational movements of the telescopic arm about a longitudinal axis of said arm. This gives the tools positioning freedom without changing their basic orientation.

According to one embodiment, the attachment means of the telescopic arm on the second bearing structure comprises first fastening means interdependent with said second bearing structure bearing against an upper face of said second bearing structure. This upper face of the second bearing structure extends generally in a plane substantially perpendicular to a longitudinal axis of the telescopic arm, so that the telescopic arm, the tool mounted at the end of said telescopic arm and any load on said tool exert bearing forces on said upper face via the first fastening means.

Preferably, the first fastening means of the attachment means of the telescopic arm on the second bearing structure comprises an intermediate support designed to be fixed interdependently to the second bearing structure, said attachment means comprising at least one bearing part interdependent with said telescopic arm bearing on said intermediate support and allowing pendular movements of said telescopic arm. In this way, the attachment means can take up the lifting forces exerted on the second bearing structure through the telescopic arm while lifting the tool and its potential load.

It should be noted that the tools can be actuated by actuating means, generally hydraulic cylinders or cable lifting means, whose function is both to maintain the active tool at the desired level, and to lift this tool and any loads handled by this tool. Generally, the line of action of said actuation means is coincident with the longitudinal axis of the telescopic arm carrying the tool. The forces exerted by these actuating means are generally lifting forces, i.e. forces adding to the weight of the tool, the telescopic arm on which it is mounted and any load being handled by this tool. The descending forces exerted by the actuating means are usually minimized due to the weight of the tool itself and its telescopic arm. In this way, the presence of at least one bearing point on the upper face of the second bearing structure is theoretically sufficient to take up the lifting forces exerted by the tools.

Preferably, the at least one bearing part (in this case both bearing parts) includes a fuse designed to break when the amplitude of the pendular movements of the telescopic arm is outside a predetermined range of tolerance. The material and shape of this fuse element are chosen so as to limit the forces having a horizontal component transmitted to the second bearing structure. In other words, the fuse element is designed to be broken before risking damage to the fixed component of the telescopic arm or the second bearing structure.

Preferably, the attachment means of the telescopic arm onto the second bearing structure includes second fastening means interdependent with the attachment portion of the fixed member of said telescopic arm, said second fastening means comprising two uprights oriented substantially parallel to the longitudinal axis of the telescopic arm.

Preferably, the attachment means comprises two bearing parts interdependent with the telescopic arm bearing on the intermediate support and allowing pendular movements of said telescopic arm, the fuse element of each bearing part being fixed interdependently onto each upright of the second fastening means respectively.

Another subject of the invention is a pot tending machine comprising a carriage and a pot tending module as described above.

Yet another subject of the invention is a pot tending assembly for a plant producing aluminum by igneous electrolysis including an overhead traveling crane and at least one pot tending machine according to the invention.

Yet another subject of the invention is the use of a pot tending assembly according to the invention for work on electrolytic cells for the production of aluminum by igneous electrolysis.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 is a cross-sectional view of a typical electrolysis hall for the production of aluminum and including a pot tending module shown schematically.

FIG. 2 is a side view of a pot tending machine according to one embodiment of the invention.

FIG. 3 is a perspective view of the same pot tending machine as that shown in FIG. 2.

FIG. 4 is a perspective view of the pot tending module of the pot tending machine shown in FIG. 2.

FIG. 5 is a sectional view of connecting means between said arm and the second bearing structure.

FIG. 6 is a partial view of the upper part of the fixed member of a telescopic arm and the mechanical connecting device for connecting said arm to the first bearing structure.

FIG. 7 is a sectional view of part of the mechanical connecting device for connecting said arm to the first bearing structure.

DETAILED DESCRIPTION OF THE INVENTION

Electrolysis plants for the production of aluminum include a liquid aluminum production area containing one or more electrolysis halls 1. As illustrated in FIG. 1, each electrolysis hall 1 has electrolytic cells 3 and at least one “pot tending assembly” or “pot tending machine” 5. The electrolytic cells 3 are normally arranged in rows or lines, each row or line typically comprising more than one hundred cells. Cells 3 are arranged so as to leave free an aisle 7 along the electrolysis hall 1. Cells 3 include a series of anodes 9 provided with a metal stem 11 for the fixing and electrically connecting the anodes to a metal anode frame (not shown). The pot tending assembly 5 is used to carry out operations on the cells 3 such as changing anodes or filling the electrolytic cell feed hoppers, aluminum fluoride, for example. It can be also used to handle various loads, such as cell parts, ladles of molten metal or anodes. The invention particularly concerns pot tending assemblies used to make anode changes.

The pot tending assembly 5 comprises an overhead travelling crane 13 which may be translated above the electrolytic cells 3, and along them, and a pot tending machine 15 comprising a movable carriage 17 able to be moved on the overhead travelling crane 13 and a pot tending module 19 equipped with several handling and servicing components such as 21 tools (shovels, extraction keys, crust breakers, etc.). The overhead traveling crane (13) rests and circulates on gantry tracks 23, 24 laid out in parallel with each other and with the main axis of the hall (and the line of cells). The overhead traveling crane 13 can thus be moved along the electrolysis hall 1.

As illustrated in FIGS. 2 and 3, the pot tending module 19 comprises a frame 25, typically a platform capable of being attached to the carriage 17 and a rotary part or turret 33 mounted on the frame 25 so as to be pivotable around a vertical axis A when in use. The turret 33 is normally equipped with a balcony or a cab, not shown, with commands to maneuver the module 19 and the handling and servicing components 21, 22. The tools are normally on the same side of the turret 33, namely the side which is located below the turret when in use.

The carriage 17 of the pot tending assembly 5 is mounted on roller devices 31, 32 designed to allow the carriage on the gantry track of the overhead travelling crane 13. The frame 25 of pot tending module 19 is attached to the carriage 17. The rotary part or turret 33 of pot tending module 19 is mounted on frame 25 so as to rotate around itself around the substantially vertical axis A shown in FIGS. 3 and 4. Specifically, the rotary part 33 is suspended beneath the frame 25 of the pot tending module.

As illustrated in FIGS. 2, 3 and 4, the rotary part 33 of pot tending module 19 comprises a first bearing structure 35 designed to carry all of said rotary part. This first bearing structure 35 is mounted on frame 25 so as to pivot about the substantially vertical axis A shown in FIGS. 3 and 4. Specifically, the first bearing structure 35 is suspended beneath the frame 25 of the pot tending module. In this way, the first bearing structure 35 constitutes the upper part of the rotary part 33.

The rotary part 33 of the pot tending module 19 further includes a hopper 37 for supplying an electrolytic cell with products in powder form, said hopper being carried by the first supporting structure 35. As explained above, the inclusion of this hopper 37 in the rotary part 33 minimizes the volume under the frame 25 of the pot tending module, or more precisely the spatial dimensions of the pot tending module.

The rotary part 33 of the pot tending module 19 is equipped with several handling and servicing components generally comprising a set of tools mounted on telescopic arms. In the embodiment illustrated in FIGS. 2, 3 and 4, the determined set of tools includes a crust shovel 21 and an anode handling clamp 22. This set of tools may also include, among other things, a crust breaker. These tools are designed for anode changing operations on the electrolytic cells. In these operations, the crust breaker is used to break the alumina crust and solidified bath which generally covers the anodes of the cell, the crust shovel 21 is used to clear the location of the anode, after removal of the worn anode, by removing the solid materials therein, and the anode handling clamp 22 is used to grasp and manipulate the anodes by their stems, particularly to remove the worn anodes from an electrolytic cell and to fit new anodes into the electrolytic cell. The rotary part 33 of the pot tending module 19 may also include other tools, which are not shown, such as a second anode handling clamp, an alumina or crushed bath feeder device comprising a retractable duct, or a hoist.

The telescopic arm on which each tool is mounted means any device comprising at least one fixed member, typically a hollow shaft or an elongated chassis, and a movable member, typically a stem or a hollow shaft, able to be moved relative to the fixed member along a predetermined axis, which is generally parallel to the main axis of the fixed member. The fixed member is fixed to the pot tending module, namely the rotary part 33 of the pot tending module 19. The tool is fixed to the movable member, generally at one end thereof. In the embodiment illustrated in FIGS. 2, 3 and 4, each telescopic arm 39 comprises a first hollow shaft of substantially square section and a second hollow shaft of substantially square section able to slide inside the first hollow shaft. The main axis of the first and second hollow shafts coincide. The main axis of each telescopic arm is generally designed to be substantially vertical when in use and is typically parallel to the axis of the fixed member of the same telescopic arm. In other embodiments not shown, the telescopic arm of each tool may include one or more additional intermediate members located between the fixed member and the movable member and able to slide relative to these.

The fixed member of the telescopic arm of each of these tools 21, 22, i.e. the hollow shaft 39 in which a movable member of said telescopic arm slides, is mounted on a second bearing structure 41. This second bearing structure is interdependent with the rotary part 33 and separate from the first bearing structure 35. This second bearing structure 41 is arranged under the hopper 37. In this case, the second bearing structure 41 can also carry a walkway placed below the hopper which can be equipped with a hydraulic unit and electrical cabinets. The walkway allows maintenance operators access to tools and various components of the pot tending module.

Specifically, as can be seen in FIGS. 2, 3 and 4, the hollow shaft 39 of each telescopic arm is mounted on the second bearing structure 41 via attachment means 43 allowing pendular movements of said telescopic arm while prohibiting rotation of the same telescopic arm about its longitudinal axis. These pendular movements of the telescopic arms prevent jolting to a tool from directly affecting the entire rotary part 33, and in particular other tools carried by the same rotary part.

Unlike the pot tending module of prior art, the hollow shaft 39 of each telescopic arm is not attached to the second bearing structure 41 by one of its ends. The attachment means 43 are in fact attached to an attachment part of hollow shaft 39 which is placed at a distance from the ends of said hollow shaft, i.e. at a distance from the upper end and the lower end of said hollow shaft. The upper ends of hollow shafts 39 of the telescopic arms carrying the anode handling clamp 22 and the bucket shovel 21 are shown in FIG. 2 as reference 45. The lower ends of hollow shafts 39 of the same telescopic arms are shown in FIGS. 2, 3 and 4 as reference 47. The hollow shafts 39 of the telescopic arms are not attached to the second bearing structure 41 by one of their ends; they are in fact arranged through openings 49 in the same second bearing structure. These openings 49 are clearly visible in FIG. 4. It should be noted that the opening 49 on the right of FIG. 4 corresponds to the location of the telescopic arm of a tool that has been dismantled. With this configuration, tool positioning accuracy is improved. Another advantage of this configuration is to limit the space required under frame 25 of the pot tending module 19.

As shown in FIG. 5, the attachment means 43 of each telescopic arm on the second bearing structure 41 comprise first fastening means 51 interdependent with the same second bearing structure 41 bearing against an upper face 53 of said second structure. These first fastening means 51 allow the telescopic arm and the tool to be carried. Specifically, the first fastening means 51 are suspended from the second bearing structure 41. This allows assembly and disassembly of the telescopic arm from below said second bearing structure 41 by an operator positioned on a walkway of this same second bearing structure. The first fastening means 51 of the attachment means 43 comprise an intermediate support 55 to be fixed interdependently with the second bearing structure 41 by means of bolts 57 and nuts 58.

The attachment means 43 includes two bearing parts 61 fixed to the hollow shaft of the telescopic arm 39 and resting on the intermediate support 55 allowing pendular movement of said telescopic arm. Each bearing part 61 comprises a fuse element 63 designed to break when the forces exerted by the telescopic arm on the second bearing structure 41, in particular the horizontal component of these forces, is outside a predetermined tolerance range. The attachment means 43 of the telescopic arm on the second bearing structure 41 comprise second fastening means 65 interdependent with the attachment part of the hollow shaft 39 of this same telescopic arm. These second attachment means comprise, in this case, two uprights 67 oriented substantially parallel to the longitudinal axis of the telescopic arm.

Each tool 21, 22 is actuated by a hydraulic cylinder 62, shown in FIG. 4, the line of action of which is coincident with the longitudinal axis of the telescopic arm carrying the tool. The forces exerted by the cylinders 62 are generally lifting forces, i.e. forces added to the weight of the tool, the telescopic arm on which it is mounted and any load handled by this tool. The descending forces exerted by the cylinders 62 are usually minimized due to the weight of the tool itself and its telescopic arm. In this way, the presence of at least one bearing point on the upper face 53 of the second bearing structure 41 is theoretically sufficient to take up the lifting forces exerted by the tools via the bearing parts 61.

As can be seen in FIG. 4, the hollow shaft 39 of the telescopic arm of each tool 21, 22 is connected to the first bearing structure 35 by a mechanical connecting device 71 to further limit the amplitude of the pendular movements of said telescopic arm. The horizontal deflection of the telescopic arm and of the tool carried by said arm is thereby limited and the tolerance range of the amplitude of the pendular movements of the telescopic arm is better controlled. With this configuration of the pot tending module 19, the radial or horizontal components of forces exerted by each telescopic arm are partly taken up by the first bearing structure 35, through the mechanical connecting device 71.

In the example shown in FIGS. 2, 3 and 4, the mechanical connecting device 71 is mounted to connect the upper end 45 of hollow shaft 39 of each telescopic arm to the first bearing structure 35. In particular, the upper end 45 of hollow shaft 39 of each telescopic arm has an elevation just below that of the frame. For this, the part of the hollow shaft 39 between its upper end 45 and its attachment part extends through an opening 73 in the first bearing structure 35.

As can be seen in FIG. 6, the mechanical connecting device 71 between the hollow shaft or fixed member 39 of the telescopic arm of each tool and the first bearing structure 35 comprises two damping systems 75, 76 to limit the amplitude of the pendular movements of the telescopic arm in two mutually perpendicular horizontal directions. Each damping system is designed to take up the movement of the hollow shaft 39 along one or the other horizontal direction. Each damper system also helps to center hollow shaft 39, or rather to return it to a centering position.

As can be seen in FIG. 7, each damper system 75, 76 acting in a given horizontal direction comprises a movable part 79 that is interdependent with the hollow shaft 39 of a telescopic arm, and a deformable part 81 cooperating with said movable part 79 and with two walls 83, 84 interdependent with the first bearing structure 35, to take up any horizontal movement in the given horizontal direction. The deformable part 81 has an axial spring 85 acting at its ends on two mobile stops 87, 88 cooperating with the two walls, 83, 84 respectively interdependent with the first bearing structure 35. The movable part 79, interdependent with hollow shaft 39, has two annular parts 89, 90 designed to slide along the sleeves formed on both mobile stops, 87, 88 respectively, resting on one or the other of said stops according to the movement of the hollow shaft 39. These annular parts 89 also keep the two mobile stops 87, 88 in contact with the ends of the spring 85.

With this damping system 75, 76, any movement of the hollow shaft 39 of a telescopic arm and the movable part 79 interdependent with said hollow shaft is accompanied by a deformation of the deformable part 81 by compressing the spring 85 via one or other annular part 89, 90 and the mobile stop 87, 88 on which said annular part slides. At the same time, the same mobile stop 87, 88 is separated from the wall 83, 84 interdependent with the first bearing structure 35, while the opposite mobile stop 88, 87 rests more heavily on the other wall 84, 83 interdependent with the same bearing structure. The mobile part 79 and the hollow shaft 39 of the telescopic arm are then returned to their initial position by a spring 85. In this way, the tolerance range of the amplitude of the pendular movement of hollow shaft 39 of each telescopic arm is better controlled. 

1. Pot tending module for use in a plant for producing aluminum by igneous electrolysis, said module comprising a frame able to be secured to a carriage and a rotary part mounted on said frame so as to pivot about a substantially vertical axis, said rotary part being equipped with at least one tool mounted on a telescopic arm of said rotary part, said pot tending module further comprising a first bearing structure mounted on said frame and designed to bear a hopper, said pot tending module being characterized in that said first bearing structure and said hopper are included in said rotary part, said first bearing structure being designed to bear all of said rotary part and being mounted on said frame so as to pivot about said substantially vertical axis, and in that said rotary part comprises a second bearing structure, a fixed member of said telescopic arm being mounted on said second bearing structure interdependent with said rotary part through attachment means allowing pendular movements of said telescopic arm, said attachment means being fixed to an attachment part of said fixed member placed at a distance from the ends of said fixed member.
 2. Pot tending module according to claim 1, characterized in that the fixed member of the telescopic arm is connected to the first bearing structure by a mechanical connecting device that limits an amplitude of the pendular movements of said telescopic arm.
 3. Pot tending module according to claim 2, characterized in that the attachment part of the fixed member of the telescopic arm is at a distance from an upper end of said fixed member, the distance being greater than one tenth of the length of said fixed member.
 4. Pot tending module according to claim 2, characterized in that the mechanical connecting device is mounted to connect an upper end of the fixed member to the first bearing structure.
 5. Pot tending module according to claim 2, characterized in that the mechanical connecting device comprises at least one damping system to limit the amplitude of the pendular movements of the telescopic arm in a horizontal direction.
 6. Pot tending module according to claim 5, characterized in that the mechanical connecting device has two damping systems to limit the amplitude of the pendular movements of the telescopic arm in two substantially perpendicular horizontal directions.
 7. Pot tending module according to claim 1, characterized in that an upper end of the fixed member of the telescopic arm has an elevation just below that of the frame.
 8. Pot tending module according to claim 1, characterized in that a part of the member fixed between an upper end of the fixed member and the attachment part extends through an opening in the first bearing structure.
 9. Pot tending module according to claim 1, characterized in that the attachment means are designed to prevent rotational movements of the telescopic arm about a longitudinal axis of said telescopic arm.
 10. Pot tending module according to claim 1, characterized in that the rotary part is equipped with a determined set of tools, each tool of said determined set being mounted on a telescopic arm attached to the second bearing structure.
 11. Pot tending module according to claim 10, characterized in that the determined set of tools comprises at least one tool selected from a crust shovel, an anode handling clamp and a crust breaker.
 12. Pot tending module according to claim 1, characterized in that the attachment means of the telescopic arm on the second bearing structure comprise first fastening means interdependent with said second bearing structure bearing on an upper face of said second bearing structure.
 13. Pot tending module according to claim 12, characterized in that the first fastening means of the attachment means of the telescopic arm on the second bearing structure comprises an intermediate support designed to be fixed interdependently to the second bearing structure, said attachment means comprising at least one bearing part interdependent with said telescopic arm bearing on said intermediate support and allowing pendular movements of said telescopic arm.
 14. Pot tending module according to claim 13, characterized in that at least one bearing part comprises a fuse element designed to break when the amplitude of the pendular movements of the telescopic arm is outside a predetermined range of tolerance.
 15. Pot tending module according to claim 12, characterized in that the attachment means of the telescopic arm onto the second bearing structure includes second fastening means interdependent with the attachment part of the fixed member of said telescopic arm, said second fastening means comprising two uprights oriented substantially parallel to the longitudinal axis of the telescopic arm.
 16. Pot tending module according to claim 14, characterized in that the attachment means of the telescopic arm onto the second bearing structure includes second fastening means interdependent with the attachment part of the fixed member of said telescopic arm, said second fastening means comprising two uprights oriented substantially parallel to the longitudinal axis of the telescopic arm, and further characterized in that the attachment means comprises two bearing parts interdependent with the telescopic arm bearing on the intermediate support and allowing pendular movements of said telescopic arm, and in that the fuse element of each bearing part is attached interdependently onto each upright respectively of the second fastening means.
 17. Pot tending machine for use in a plant for producing aluminum by igneous electrolysis comprising a carriage and a pot tending module comprising a frame able to be secured to the carriage and a rotary part mounted on said frame so as to pivot about a substantially vertical axis, said rotary part being equipped with at least one tool mounted on a telescopic arm of said rotary part, said pot tending module further comprising a first bearing structure mounted on said frame and designed to bear a hopper, said pot tending machine being characterized in that said first bearing structure and said hopper are included in said rotary part, said first bearing structure being designed to bear all of said rotary part and being mounted on said frame so as to pivot about said substantially vertical axis, and in that said rotary part comprises a second bearing structure, a fixed member of said telescopic arm being mounted on said second bearing structure interdependent with said rotary part through attachment means allowing pendular movements of said telescopic arm, said attachment means being fixed to an attachment part of said fixed member placed at a distance from the ends of said fixed member.
 18. Pot tending assembly for a plant for producing aluminum by igneous electrolysis comprising an overhead traveling crane and at least one pot tending machine comprising a carriage and a pot tending module comprising a frame able to be secured to a carriage and a rotary part mounted on said frame so as to pivot about a substantially vertical axis, said rotary part being equipped with at least one tool mounted on a telescopic arm of said rotary part, said pot tending module further comprising a first bearing structure mounted on said frame and designed to bear a hopper. said pot tending assembly being characterized in that said first bearing structure and said hopper are included in said rotary part, said first bearing structure being designed to bear all of said rotary part and being mounted on said frame so as to pivot about said substantially vertical axis, and in that said rotary part comprises a second bearing structure, a fixed member of said telescopic arm being mounted on said second bearing structure interdependent with said rotary part through attachment means allowing pendular movements of said telescopic arm, said attachment means being fixed to an attachment part of said fixed member placed at a distance from the ends of said fixed member.
 19. Method comprising using a pot tending assembly for work on electrolytic cells for the production of aluminum by igneous electrolysis, wherein the pot tending assembly comprises an overhead traveling crane and at least one pot tending machine comprising a carriage and a pot tending module comprising a frame able to be secured to a carriage and a rotary part mounted on said frame so as to pivot about a substantially vertical axis, said rotary part being equipped with at least one tool mounted on a telescopic arm of said rotary part, said pot tending module further comprising a first bearing structure mounted on said frame and designed to bear a hopper, said pot tending module being characterized in that said first bearing structure and said hopper are included in said rotary part, said first bearing structure being designed to bear all of said rotary part and being mounted on said frame so as to pivot about said substantially vertical axis, and in that said rotary part comprises a second bearing structure, a fixed member of said telescopic arm being mounted on said second bearing structure interdependent with said rotary part through attachment means allowing pendular movements of said telescopic arm, said attachment means being fixed to an attachment part of said fixed member placed at a distance from the ends of said fixed member. 